Shrinking Arctic sea ice may have helped cause unusually snowy winters that have blanketed parts of the Northern Hemisphere in recent years. That's the conclusion of a new study that suggests such winter blasts may become more frequent as warming further shrinks sea ice.

"We think there's probably a linkage between the record decline of Arctic sea ice and record snowfall over much of the northern continents," said lead author Jiping Liu, a senior research scientist at the Georgia Institute of Technology, whose work was published yesterday by the Proceedings of the National Academy of Sciences.

Large portions of the United States were battered by heavy snowfall during the winters of 2009 and 2010, while much of Europe has been unusually snowy this year. At the same time, the Arctic's sea ice cover has receded rapidly. The area covered by sea ice shrunk to its lowest extent on record in the summer of 2007, and subsequent years round out the list of the five lowest sea ice extents on record since satellite monitoring began in 1979.

Liu and his colleagues believe there are two processes that link the thawing Arctic and harsh winters at lower latitudes, based on their analysis combining records of Arctic sea ice cover and climate modeling.

A 'wavier' Jet Stream

"If there is a dramatic loss of Arctic sea ice, the westerly winds that blow across the North Pacific and North Atlantic oceans are weakened," he said. "This means we will have a wavier Jet Stream."

That wavier Jet Stream brings more cold air to lower latitudes, including the northern United States, central and eastern Europe, and northern and central China, even as it warms Greenland and northeastern Canada.

Receding sea ice also leaves more ocean surface exposed to warm surface air in the summer and autumn, which leads to more water vapor in the atmosphere -- water vapor that is funneled south via the Jet Stream, where it fuels heavy snows.

The new study suggests that a summer thaw of 1 million square kilometers of Arctic sea ice corresponds to a 3-12 percent increase in snow cover in parts of the United States, Europe and China. Liu is reluctant to ascribe the phenomenon to climate change, however, noting that the rapid decline in Arctic sea ice began just five years ago, in 2007.

"If we see this pattern year after year, then we can say it's due to climate change," he said.

Previous studies have linked the recent drop in Arctic sea ice cover and thickness to man-made warming. They include a series of annual "Arctic report cards" issued by the National Oceanic and Atmospheric Administration, which have found widespread evidence that climate change is driving the continued decline of Arctic summer sea ice, shortening the region's snow season, warming land surfaces and permafrost and changing the population and habitat of Arctic wildlife.

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